Circadian changes in the abomasal secretions of the preruminant calf

The purpose of this study was to investigate the circadian changes in the abomasal secretions (quantities of juice, enzymes and electrolytes) of the preruminant calf.The gastric juice was collected every hour from five calves fitted with an innervated abomasal pouch and given milk twice daily, with a 7-h interval between the morning and the evening meals.The amounts of gastric secretions produced were steady during 24 h, except for changes after the meals.The morning meal caused a considerable increase in secretions of electrolytes and enzymes.The values of CI-, H + , Na+ + and K + ions, chymosin and pepsin in the first postprandial hour were 3.8, 4.1, 3.5, 2.6, 2.4 and 2.1 times higher, respectively, than those of the 24th hour used as prefeeding levels.The influence of the evening meal on secretions of CIand Na + ions and enzymes was less marked and also more delayed for all electrolytes.Variations in the amounts secreted per hour appeared to be greater for H + + ions than for enzymes, thus the ratios between maximal and minimal quantities observed during the 24-h cycle were 4.6 for H + ions and 2.8 for chymosin. Introduction.The abomasum of the calf corresponds to the stomach of monogastric animals ; in fact, it is the only functional gastric reservoir in the preruminant animal.Milk is ingested during short-lasting meals (usually less than 3 min in the bucket-fed-calf).The abomasum not only serves as a reservoir, but it also participates in digestion (Guilloteau et al., 1981) and therefore its secretions adapt to meal frequency.Furthermore, it may be assumed that this organ, like the pancreas, possesses its own secretory rhythm independent of feeding (Davicco, 1978).To our knowledge, the effect of a meal on the secretion of certain gastric juice components has only been studied over some hours (Ash, 1964 ; Hill, Noakes and Lowe, 1970 ; Rusev, Petrov and Bocheva, 1971 ; Williams, Roy and Gillies, 1976) and never throughout a whole day.